By DORIE STOLLEY/ecoRI News contributor

Rainbow smelt are similar in lifestyle to the alewife and blueback herring. These diminutive forage fish are anadromous — they hatch in fresh water, travel to the ocean to grow to adulthood, then return annually to their natal waters to reproduce. They were once widely celebrated throughout coastal Massachusetts in late winter for their savory flavor. Hordes were caught, coated in flour, fried and eaten with gusto.

Now, only a few tenacious fishermen and their families experience this delight. Overfishing, pollution and dams are a few of the factors to blame for the decline of this once regionally important fish.

Two centuries ago, rainbow smelt spawned in rivers as far south as the Chesapeake Bay in Virginia; now their southernmost spawning area is Buzzard’s Bay. Rainbow smelt numbers have been dropping since the 1800s, when people caught them in nets by the thousands during late-winter spawning runs. Harvesting large numbers of fish before they were allowed to reproduce in this manner was blamed for a noticeable decrease in smelt numbers, and in 1886 the state Legislature banned the taking of smelt by net during spawning runs.

By 1874, all methods of fishing for rainbow smelt, except hook and line, were forbidden year-round in all but a few rivers. While some local smelt fisheries reported a rebound, statewide the decline continued until 2004, when the National Oceanographic and Atmospheric Administration (NOAA) declared them a federal species of concern. Now, work is underway to better understand the reasons for the decline and to restore their numbers across Massachusetts, New Hampshire and Maine.

To restore rainbow smelt, their basic spawning needs must be met. This can be summed up in a few words: clean, flowing water. To a rainbow smelt, clean water means low levels of dissolved contaminants, nutrients and sediment, all of which can kill their vulnerable eggs. Flowing water means enough water to swim in, as well as the absence of obstacles, such as dams or improperly positioned culverts, which can impede movement upstream to prime spawning areas of fast-flowing, highly oxygenated water.

Work to benefit rainbow smelt also betters the health of rivers, by delivering a myriad benefits to other wildlife, to humans and to the watershed as a whole. For instance, removing derelict dams allows smelt, river herring and other migratory fish to move freely along the river; decreases the risk of catastrophic flooding; removes liability to the dam owner and mosquito breeding habitat; and increases recreational opportunities.

The state of Massachusetts is working with New Hampshire and Maine to develop a regional plan to conserve and restore rainbow smelt habitat. Most of the measures are relatively easy, such as leaving stream-side vegetation in place or planting stream-side trees and shrubs. Other measures provide both cost savings and habitat benefits, such as using minimal fertilizer on lawns and gardens, and asking your city or town to reduce its use of road salt and sand near streams.